Starting circuit for fluorescent lamps



D. s. GUSTIN ETAL 2,355,968

STARTING CIRCUIT FOR FLUORESCENT LAMPS Aug. 15, 1944.

Filed June 19, 1942 INVENTORS TTQRNEY lfatented Aug. 15, 1944 UNITED STARTING CIRCUIT FOR FLUORESCENT LAMPS Daniel S. Gustin, Bloomfield, and Nelson H.

Bryant, East Orange, N. 1., assignors to Westingliouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation oi Pennsylyania Application June 19, 1942, Serial No. 447,646

Claims.

The present invention relates to gaseous electric discharge lamps and more particularly to a circuit arrangement whereby such lamps may be instantaneously started from a source 0i supply of the customary domestic potential.

- A. commonly recognized phenomenon oi such discharge lamps is that they require a much higher voltage to initiate a discharge than to sustain the same. Numerous arrangements have been employed in the prior art all of which are subject to various disadvantages such, for example, as the apparatus not having good operating characteristics and the high voltage peaks in many instances very seriously damaging the lamp electrodes.

It is accordingly an object of the present invention to provide a circuit arrangement for gaseous discharge lamps which may be instantaneously started from a source or supply of the customary domestic potential and without causing any damage to the lamp electrodes.

Another object of the present invention is the provision of a circuit arrangement for gaseous discharge lamps wherein the lamps are operated in a series circuit substantially in resonance and in which the lamps are started substantially instantaneously from a source of supply 01 the customary domestic potential.

Still further objects oi the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 is a schematic illustration of the starting and operating circuitior gaseous discharge lamps in accordance with the present invention;

Fig. 2 is a schematic illustration otia modification which the starting and operating circuit of the resent invention may take, and

Fig. 3 is a schematic illustration of other modihcation'which the present invention may take. I

Referring now to the drawing in detail, a pair of gaseous discharge lamps I and I of approximately 40 watt size are shown, with the lamp I being provided with a pair oi filamentary electrodes l and I andthe lamp 6 having similar electrodes 8 and It. The electrodes I and 9 at the end oi each lamp are connected in a series heating circuit to the source of supply Ll--L2 of the customary domestic potential of 220 volts, which may be directly from the line or from the. secondary winding of a transformer, the primary winding of which is connected to .a 110- volt line. This circuit extends from one side of the source of supply Li through an inductance still ani2 and capacitance ii to one end of the ills.- mentary electrode 1 and from the opposite end of such electrode through an impedance device such as another inductance ii, to the filamentary electrode 9, and thence back to the opposite side of the source of supply L2. The other remaining electrodes 8 and iii are connected together by a conductor I5. r

The circuit thus formed constitutes a series heating circuit for the filamentary electrodes 1 ands, as above mentioned, which is at or near resonance with the fundamental frequency of the source, and while the lamps themselves are in series relation with each other and the source of supply LI-LI, they may be said to form a parallel or shunt circuit with respect to the series heating circuit for the filamentary electrodes 7 and 9. Accordingly with inductance of the element I! being about 0.5 henry, that of element [4 about 2.5 henries, and the capacitance of the condenser l3 approximately 3.0 microfarads, a current of approximately .465 ampere at about 90% normal line voltage flows in the heating circuit, upon closure of the switch l6, which very rapidly heats the filamentary electrodes I and 8 to an electron-emitting temperature.

This causes a voltage dropoi' about 450 volts across the impedance or inductance H which voltage is sufliciently high to start a discharge in the series connected lamps 5 and 8. Once the discharge is initiated, which follows almost instantaneously upon heating of the filamentary electrodes. the circuit constants as above mentioned cause a'normal lamp current of 0.42 ampere to flow through .the lamps at normal line voltage. During operation the entire circuit consumes about 97 watts of which 80 watts are taken by the two 40-watt lamps, the remainder constituting power loss in the circuit. However, this power loss is exceptionally low in comparison with that occurring in other types of circuits and is amply compensated for by the rapidity with which the lamps are started following closur of the line switch.

In Fig. 2 a slight modification of the circuit arrangement of the present invention is shown which diners from that of Fig. 1 in that an immentary electrodes 1 and 9 are again heated very rapidly and a voltage drop of approximately 450 volts occurs across the capacitance H which is sufiicient to initiate a discharge in the series connected lamps in the same manner as above described. l'heinductance it limits the lamp current while the capacitance I1 is charging and discharging, since without it the capacitance would be connected directly across the lamps 5 and .6 without any limitation on current flow. By connecting the capacitance IS in series with the inductance l8 the impedance of the latter is effectively reduced which allows proper lamp current to flow.

The modification of Fig. 3 is practically identical to thatof Fig. 1 except that in this latter embodiment not only are the filamentary electrodes I and 9 preheated, but also the remain- 7 ing filamentary electrodes 8 and I0. To heat these latter electrodes a transformer 20 is provided having its primary winding connected in series with the impedance again taking the form of the inductance element l4, while the filamentary electrodes 8 and It are connected in series with the transformer secondary. If desired, the

inductance element It may be dispensed with and referred to in Fig. 1, and results in longer lamp life due to easier starting and less end blackening from sputtered electron emissive material. It thus becomes obvious to those skilled in the art that a starting and operating circuit for gaseous discharge lamps is herein provided in which the lamps are started practically immediately upon connection to a source of supply of the customary domestic potential. Moreover, the

circuit is substantially a resonant one and wherein the power loss is exceptionally low, thereby increasingthe overall efiiciency of the system.

1 Although several embodiments of the present invention have been shown and described, it is :to be understood that still further modifications thereof may be made without departing from the spirit and scope of the appended claims.

We claim:

- said heating circuit for the saidone filamentary' 1. In combination, a source-of electrical energy,

- a pair of gaseous discharge lamps having a starting voltage higher than the voltage of said source and each provided with at least one filamentary electrode, means to connect only one filamentary electrode of each lamp in a series heating circuit which is in electrical shunt with the discharge circuit for said lamps comprising an impedance disposed between one of said filamentary 2. In combination, a source of electrical energy,

a pair of gaseous discharge lamps having a. starting voltage higher than the voltage of said source and each provided with at least one filamentary re electrode, a series heating circuit for only one filamentary electrode of each lamp which is in electrical shunt with the discharge circuit for said lamps including an inductance disposed between one filamentary electrode of one of said lamps and the source and an imp dance interposed between the said one filamentary electrode of each lamp and subject to a voltage drop thereacross of suflicient magnitude to initiate a discharge in said lamps-and means independent of electrode for each lamp and connecting the remaining electrode of each lamp together to complete a series connected discharge circuit for said pair of lamps.

3. In combination, a source of electrical energy, a pair of gaseous discharge lamps having a starting voltage higher than the voltage of said source and each provided with atleast one filamentary electrode, a series heating circuit for only one filamentary electrode of each lamp which is in electrical shunt with the discharge circuit for said lamps including an inductace disposed between one filamentary electrode of one of said lamps and the source .and a second inductance interposed between the said one filamentary electrode of each lamp and subject to a voltage drop thereacross of sufiicient magnitude to initiate a discharge in said-lamps, and means independent of said heatingcirouit for the said one filamentary electrode for each lamp and connecting the remaining electrode of each lamp together to complete a series connected discharge circuit for said pair of lamps.

4. In combination, a source of electrical energy, a pair of gaseous discharge lamps having a starting voltage higher than the voltage of said source and each provided with at least one filamentary electrode, a series heating circuit for only one filamentary electrode of each lamp which is in electrical shunt with the discharge circuit for said lamps including an inductance disposed between the'said one filamentary electrode-of one of said lamps and the source and capacitance interposed between the said one filamentary electrode of each lamp and subject to a voltage drop thereacross of suflicient magnitude to initiate a discharge in said lamps, and means independent of said heating circuit for the said one filamentary electrode for each lamp and connecting the remaining electrode of each lamp together to complete a series connected discharge circuit for said pair of lamps.

5 In combination, a source of electrical energy, a pair of gaseous discharge lamps having a starting voltage higher than the voltage of said source and each provided with at least one filamentary electrode, a series heating circuit for only one filamentary electrode of each lamp which is in electrical shunt with the discharge circuit for said lamps including an impedance disposed between the said one filamentary electrode of one of said lamps and the source and a second impedance interposed between said one filamentary electrode of each lamp and subject to a voltage drop thereacross of suflicient magnitude to initiate a discharge in .said lamps, and another impedance independent of said heating circuit for the said one filamentary electrode for each lamp and connecting the remaining electrode of each lamp together to complete a series connected discharge circuit for-said pair of lamps.

DANIEL. S. GUSTIN. NELSON H. BRYANT. 

